Distinct Morphological Features Predictive for Aggressiveness of Papillary Thyroid Microcarcinoma: a Study of 72 Cases and 80 Tumor Foci

Introduction: In this study, we aimed to investigate the importance of some distinctive morphological parameters in predicting the extrathyroidal extension, as marker of aggressiveness, in a series of papillary thyroid microcarcinoma (PTMC) cases.
Material and methods: All consecutive PTMC cases, sized ≥5mm, registered at the Department of Pathology, Tîrgu-Mureş Emergency County Hospital from January 2002 to December 2013 were re-evaluated. The following histological features were noted: the multifocality, the extrathyroidal extension, the histologic variant, the tumor’s border (well circumscribed versus infiltrative), the PTC nuclear features (well developed versus subtle), the tumor associated stromal reaction (fibrosis/desmoplasia/sclerosis versus none of these changes), the presence of “plump pink” cells, psammoma bodies, intratumoral lymphocytic infiltrate, cystic change, back-to-back arrangement, intratumoral multinucleated giant cells and lymph node involvement.
Results: Our study included 72 PTMC cases, summing up to a total of 80 PTMC foci. We have shown that extrathyroidal extension is significantly associated with the presence of “plump pink”cells (p=0.0019), well developed nuclear features of PTC (p=0.018) and tumor associated stromal reaction (fibrosis/dezmoplazia/sclerosis) (p<0.0001). Other parameters were more prevalent among PTMC foci with extrathyroidal extension, but did not reach statistical significance.
Conclusion: Our results pointed out the importance of a distinct set of morphological microscopical parameters, predictive for extrathyroidal extension in PTMC cases (“plump pink” cells, well developed PTC nuclear features, tumor associated stromal reaction, infiltrative tumor borders and conventional PTC histology). All these parameters are important to be mentioned in the histopathological reports, as they might be associated with a more aggressive biological behaviour.